Facebook can used against you

It was reported that the university authorities are using facebook to throw the book at students at Oxford University. The student union are urging students to tighten their security settings so that not much details can be viewed.

Have a look at: http://news.bbc.co.uk/1/hi/education/6902333.stm

Also in a news article, I saw these interesting facts:
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* A survey of 600 British companies showed that 1 in 5 had logged on to Facebook and similar websites to vet potential workers.
* Five students were banned from a school trip in Toronto after disparaging remarks about teachers were found on Facebook.
* A US consultancy rejected an applicant after reading that is interest included "smokin' blunts with the homies"

To be fair, I've started using facebook to catch up on old friends. But trying to keep myself as anonymous as possible. If you can call it that. But I am beginning to find already, it's not what *you* put on facebook that could give information leakage. It's what other people put in their facebooks about you. e.g. photos, etc.
But as I say to myself. There's enough information out there about me to paint a picture. But nothing substantial.